Best rule of thumb for breaking in speakers is to just to let them play for some 150/200 hours with whatever you want to throw at them - any time before this will only leave you disappointed and also leave you wondering whether yr new speakers are not sounding as good as yr previous ones and whether you have not made a mistake in buying them in the first place !
( sound familiar to anyone ?)
After this period and exercising extreme patience whilst this is happening , they will eventually give you what you what you expected from them .

I might add that this rule of thumb generally applies to all your equipment , whether electronics , speakers or cables .